Density Functional Theory Study on Structural and Energetic Characteristics of Graphite Intercalation Compounds

The structures and energetics of a number of graphite intercalation compounds (GICs) having a relatively wide range of chemistry have been investigated by density functional theory calculations with the van der Waals correction using the dispersion correction method within the framework of generalized gradient approximation. The GICs studied included potassium-intercalated graphite (KC n ), lithium-intercalated graphite (LiC n ), lithium solvated by dimethyl sulfone (DMSO)-intercalated graphite (Li­(DMSO)4C n ), lithium solvated by dibuthoxy ethane (DBE)-intercalated graphite (Li­(DBE)2C n ), perchlorate (ClO4)-intercalated graphite (ClO4C n ), and hexafluorophosphate (PF6)-intercalated graphite (PF6C n ). Our calculations show reasonable agreement with experimental data for the interlayer distances of the GICs. A correlation between the size of the intercalate and the interlayer distance of the GIC has been observed. Our study has also predicted that all the GICs studied here are energetically stable except for Li­(DBE)2C n , consistent with experimental observations. Our results have suggested that there is a strong correlation between the intercalation energy and the electron transfer between the intercalate and graphite. On the basis of our results, we propose that the ionization potential or the electron affinity of the intercalate, along with the size of the intercalate, is a good measure for the stability of the resulting GIC in general.